In clinical practice, hemodynamic monitoring during anesthesia and in intensive care units is often employed. The goal of hemodynamic monitoring is to guide interventions as well as to ensure adequate end organ perfusion and oxygen delivery by optimizing stroke volume (SV) and cardiac output (CO). Conventional hemodynamic variables such as arterial blood pressure, central venous pressure, and urine output are frequently used as surrogates for adequate end organ perfusion. However, these parameters are not able to directly measure SV and, hence, CO. Although the pulmonary artery catheter (PAC) is still considered the gold standard to monitor SV and CO, its invasive nature and potential for life-threatening complications largely restrict its use in the modern era. Recently, multiple non-invasive or minimally-invasive SV/CO monitoring devices have been introduced into clinical practice, such as pulse contour analysis devices, esophageal Doppler devices, the partial carbon dioxide rebreathing technique, and transthoracic electrical bioimpedance measurements. However, they have not yet replaced PACs due to poor trending ability and inadequate agreement with the clinical standard (e.g., PAC). Meanwhile, echocardiography, transesophageal (TEE) or transthoracic (TTE), has become a frequently utilized monitoring method, especially in cardiac operating rooms and intensive care units. TEE-based SV/CO has been validated against PAC-based values with good limits of agreement. While ultrasound-based techniques have a number of advantages, they have several important limitations, such as the difficulty of continuous real-time monitoring, interference from electric cautery, and operator dependence. Moreover, TEE is an invasive technique and is poorly tolerated by un-sedated patients. In addition, another drawback of TEE compared to pulmonary artery catheters is the inability to measure real-time SV and CO. There have been reports of continuous CO measurements based on pulse transit time, which is inexpensive and easy to use but showed poor agreement with gold standard. Therefore, it would be advantageous to provide a device and method to estimate SV based on the PWV in patients undergoing cardiac surgery.